Liquid-jet head, method for manufacturing the same, and liquid-jet apparatus

ABSTRACT

A liquid-jet head and a manufacturing method thereof are provided. The liquid-jet head includes a channel substrate which has pressure generation chambers formed therein and communicating nozzle orifices for discharging liquid droplets, and piezoelectric elements. The piezoelectric element includes a lower electrode, a piezoelectric layer and an upper electrode, and disposed on one surface of the channel substrate via a vibration plate, wherein at least pattern regions of the respective layers which constitute the piezoelectric element are covered with an insulating film formed of an inorganic insulating material.

TECHNICAL FIELD

The present invention relates to a liquid-jet head and to a method formanufacturing the liquid-jet head, as well as to a liquid-jet apparatus.More particularly, the invention relates to an ink-jet recording head inwhich a vibration plate partially constitutes pressure generationchambers communicating with corresponding nozzle orifices fordischarging ink droplets, piezoelectric elements are formed on thesurface of the vibration plate, and displacement of the piezoelectricelements causes discharge of ink droplets, and to a method formanufacturing the ink-jet recording head, as well as to an ink-jetrecording apparatus.

BACKGROUND ART

Ink-jet recording heads which have been put into practical use includetwo kinds in which a vibration plate partially constitutes pressuregeneration chambers communicating with corresponding nozzle orifices fordischarging ink droplets, and piezoelectric elements cause the vibrationplate to be deformed so as to apply pressure to ink contained in thecorresponding pressure generation chambers to thereby discharge inkdroplets from corresponding nozzle orifices. One such kind of ink-jetrecording head uses piezoelectric actuators that operate in thelongitudinal vibration mode; i.e., piezoelectric actuators that extendand contract in the axial direction of the piezoelectric elements. Theother kind of ink-jet recording head uses piezoelectric actuators thatoperate in the flexural vibration mode.

The former recording head has an advantage in that a function forchanging the volume of a pressure generation chamber can be implementedthrough an end face of a piezoelectric element abutting a vibrationplate, thereby exhibiting good suitability to high-density printing.However, the former recording head has a drawback in that a fabricationprocess is complicated; specifically, fabrication involves a difficultprocess of dividing the piezoelectric element into comb-tooth-likesegments at intervals corresponding to those at which nozzle orificesare arranged, as well as a process of fixing the piezoelectric segmentsin such a manner as to be aligned with corresponding pressure generationchambers.

The latter recording head has an advantage in that piezoelectricelements can be formed on a vibration plate through a relatively simpleprocess; specifically, a green sheet of piezoelectric material isoverlaid on the vibration plate in such a manner as to correspond inshape and position to a pressure generation chamber, followed by firing.However, the latter recording head has a drawback in that apiezoelectric element requires a certain area in order to utilizeflexural vibration, thus involving difficulty in arranging piezoelectricelements in high density.

In order to solve the drawback of the latter recording head, there hasbeen proposed an ink-jet recording head in which an even layer ofpiezoelectric material is formed over the entire surface of a vibrationplate by use of a film deposition technique, and by means oflithography, the layer of piezoelectric material is divided in such amanner as to correspond in shape and position to pressure generationchambers, thereby forming independent piezoelectric elementscorresponding to the pressure generation chambers. Piezoelectricelements formed in such a manner have a problem in that they are easilybroken because of, for example, characteristics of the externalenvironment such as moisture. In order to solve this problem, there hasbeen proposed an ink-jet recording head in which a sealing substrate(reservoir-forming substrate) having a piezoelectric-element-holdingportion is joined to a channel substrate in which pressure generationchambers are formed, and piezoelectric elements are sealed within thepiezoelectric-element-holding portion (see, for example, Patent Document1).

However, even in the case where piezoelectric elements are sealed inthis manner, there arises a problem in that when water enters thepiezoelectric-element-holding portion through a bonding portion betweenthe sealing substrate and the channel substrate, the quantity ofmoisture within the piezoelectric-element-holding portion graduallyincreases, and finally, the piezoelectric elements are broken because ofthe moisture.

Further, in order to solve the problem of the piezoelectric elementsbeing easily broken under the influence of the external environment,there has been proposed an ink-jet recording head in which a thininsulating layer formed of silicon oxide, nitrogen oxide, or an organicmaterial, preferably, a photosensitive polyimide, is formed to cover atleast a peripheral edge of the upper surface of the upper electrode ofeach piezoelectric element, and a side surface of the piezoelectriclayer thereof, and conductive patterns (lead electrodes) are formed onthe insulating layer (see, for example, Patent Document 2).

This configuration can prevent permeation of water into piezoelectricelements to some degree. However, since the conductive patterns areexposed, water may penetrate through a window where a conductive patternis connected to a corresponding upper electrode. Therefore, breakage ofpiezoelectric elements due to water cannot be prevented completely.

Further, in order to solve the problem of the piezoelectric elementsbeing easily broken under the influence of the external environment,there has been proposed an ink-jet recording head in which thepiezoelectric elements are entirely covered with a protective filmformed of an organic material whose Young's modulus of elasticity issmaller than that of the piezoelectric layer; e.g., polyimide (see, forexample, Patent Document 3). This structure can prevent breakage ofpiezoelectric elements. However, since the stress produced in theprotective film formed of the above-described material is typicallytensile stress, when piezoelectric elements are covered with such aprotective film, there arises a problem in that compression force actson the piezoelectric elements (piezoelectric layer), and the amount ofdisplacement of the vibration plate caused through drive of apiezoelectric element drops. Further, the protective film formed of anorganic material cannot prevent permeation of water unless it has aconsiderably large thickness. However, the large thickness may become aninfluential factor which hinders drive of the piezoelectric elements.

The above-described problems arise not only in ink-jet recording headswhich discharge ink droplets, but also in liquid-jet heads whichdischarge droplets of liquid other than ink.

-   Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.    2003-136734 (FIGS. 1, 2, and page 5)-   Patent Document 2: Japanese Patent Application Laid-Open (kokai) No.    H10-226071 (FIG. 2, and paragraph [0015])-   Patent Document 3: Japanese Patent Application Laid-Open (kokai) No.    2003-110160 (claims and FIG. 5)

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In view of the foregoing, an object of the present invention is toprovide a liquid-jet head which can reliably prevent breakage ofpiezoelectric elements over a long period of time, and a method formanufacturing the liquid-jet head, as well as a liquid-jet apparatus.Another object of the present invention is to provide a liquid-jet headwhich can effectively prevent a drop in the amount of displacement of avibration plate caused through drive of a piezoelectric element, and amethod for manufacturing the liquid-jet head, as well as a liquid-jetapparatus.

Means for Solving the Problems

A first aspect of the present invention which solves the above-describedproblems is a liquid-jet head characterized by comprising a channelsubstrate which has pressure generation chambers formed therein andcommunicating nozzle orifices for discharging liquid droplets; andpiezoelectric elements each of which is composed of a lower electrode, apiezoelectric layer, and an upper electrode and which are disposed onone surface of the channel substrate via a vibration plate, wherein atleast pattern regions of the respective layers which constitute thepiezoelectric elements are covered with an insulating film formed of aninorganic insulating material.

In the first aspect, since the piezoelectric layer is covered with aninsulating film formed of an inorganic insulating material, which has alow water permeability, deterioration (breakage) of the piezoelectricelements under influence of the external environment such as water(moisture) can be prevented reliably over a long period of time, withoutgreatly hindering the drive of the piezoelectric elements.

A second aspect of the present invention is the liquid-jet headaccording to the first aspect, wherein the insulating film is formed ofan amorphous material.

In the second aspect, an insulating film having a low water permeabilitycan be formed. Therefore, even when the insulating film is formed tohave a relatively small thickness, breakage of the piezoelectricelements under influence of the external environment such as water canbe reliably prevented.

A third aspect of the present invention is the liquid-jet head accordingto the second aspect, wherein the amorphous material is aluminum oxide(Al₂O₃).

In the third aspect, the piezoelectric elements are covered with aninsulating film formed of Al₂O₃ whose water permeability is considerablylow among various inorganic insulating materials. Therefore, breakage ofthe piezoelectric elements under influence of the external environmentsuch as water can be reliably prevented, without greatly hindering thedrive of the piezoelectric elements.

A fourth aspect of the present invention is the liquid-jet headaccording to the third aspect, wherein the insulating film has athickness of 30 to 150 nm.

In the fourth aspect, breakage of the piezoelectric elements underinfluence of the external environment such as water can be reliablyprevented, while displacement of the piezoelectric elements can besecured.

A fifth aspect of the present invention is the liquid-jet head accordingto the third or fourth aspect, wherein the insulating film has a filmdensity of 3.08 to 3.25 g/cm³.

In the fifth aspect, the adhesive properties of the insulating film canbe improved. Therefore, breakage of the piezoelectric elements underinfluence of the external environment such as water can be reliablyprevented, and displacement of the piezoelectric elements can besecured.

A sixth aspect of the present invention is the liquid-jet head accordingto any one of the third to fifth aspects, wherein the insulating filmhas a Young's modulus of elasticity of 170 to 200 GPa.

In the sixth aspect, breakage of the piezoelectric elements underinfluence of the external environment such as water can be prevented,and displacement of the piezoelectric elements can be secured.

A seventh aspect of the present invention is the liquid-jet headaccording to any one of the third to sixth aspects, wherein a leadelectrode for the upper electrode is formed of a material containingaluminum as a predominant component.

In the seventh aspect, the adhesion between the leads and the insulatingfilm is improved, whereby the ratio of water permeating to thepiezoelectric layer can be reduced further. Therefore, for example,breakage of the leads or defective connection with drive wiring can beprevented.

An eighth aspect of the present invention is the liquid-jet headaccording to any one of the first to seventh aspects, wherein the sum ofstress of the insulating film and stress of the upper electrode iscompressive.

In the eighth aspect, since the piezoelectric elements are covered withan insulating film, deterioration (breakage) of the piezoelectric layerunder influence of the external environment such as water (moisture) canbe reliably prevented over a long period of time. Further, since the sumof stress of the insulating film and stress of the upper electrode iscompressive, the deflection of the vibration plate is reduced, and adecrease in amount of displacement of the vibration plate can beeffectively prevented.

A ninth aspect of the present invention is the liquid-jet head accordingto the eighth aspect, wherein stress of the insulating film and stressof the upper electrode are each compressive.

In the ninth aspect, the sum of stress of the insulating film and stressof the upper electrode can be made compressive in a relatively easymanner.

A tenth aspect of the present invention is the liquid-jet head accordingto the ninth aspect, wherein the upper electrode is formed of at leastIr.

In the tenth aspect, since at least Ir is used as a material for theupper electrode, stress of the upper electrode becomes compressive.

An eleventh aspect of the present invention is the liquid-jet headaccording to the eighth aspect, wherein stress of the insulating film iscompressive, and stress of the upper electrode is tensile.

In the eleventh aspect, since the sum of stress of the insulating filmand stress of the upper electrode is compressive, the deflection of thevibration plate is reduced, and a decrease in amount of displacement ofthe vibration plate can be effectively prevented.

A twelfth aspect of the present invention is the liquid-jet headaccording to the eleventh aspect, wherein the upper electrode is formedof at least Pt.

In the twelfth aspect, since at least Pt is used as a material for theupper electrode, stress of the upper electrode becomes tensile.

A thirteenth aspect of the present invention is the liquid-jet headaccording to the eleventh or twelfth aspect, wherein stress a of theupper electrode and that of the insulating film are each represented bythe product (ε×Y×m) of Young's modulus of elasticity Y, distortion ε,and film thickness m, and stress σ₁ of the upper electrode and stress σ₂of the insulating film satisfy the condition |σ₁|<|σ₂|.

In the thirteenth aspect, since the sum of stress of the insulating filmand stress of the upper electrode is compressive, the deflection of thevibration plate is reduced, and a decrease in amount of displacement ofthe vibration plate can be prevented effectively.

A fourteenth aspect of the present invention is the liquid-jet headaccording to any one of the first to thirteenth aspects, wherein anupper-electrode lead electrode extending from the upper electrode isfurther provided, and at least pattern regions of the respective layerswhich constitute the piezoelectric elements and the upper-electrode leadelectrode are covered with the insulating film, except for regionsfacing connection portions of the lower electrode and theupper-electrode lead electrode, the connection portions being used forconnection with connection wiring.

In the fourteenth aspect, since the pattern region of theupper-electrode lead electrode, together with the piezoelectricelements, is covered with an insulating film formed of an inorganicinsulating material, which has a low water permeability, deterioration(breakage) of the piezoelectric layer (piezoelectric elements) due towater (moisture) can be reliably prevented over a long period of time.

A fifteenth aspect of the present invention is the liquid-jet headaccording to the fourteenth aspect, wherein a lower-electrode leadelectrode extending from the lower electrode is further provided, thelower electrode is connected to the connection wiring via thelower-electrode lead electrode, and the pattern region containing thelower-electrode lead electrode is covered with the insulating film,except for regions of the upper-electrode lead electrode and thelower-electrode lead electrode facing the connection wiring.

In the fifteenth aspect, since the lower-electrode lead electrode iscovered with the insulating film formed of an inorganic insulatingmaterial, permeation of water to the piezoelectric elements can be morereliably prevented.

A sixteenth aspect of the present invention is the liquid-jet headaccording to the fourteenth or fifteenth aspect, wherein the upperelectrode and the upper-electrode lead electrode are formed of differentmaterials.

In the sixteenth aspect, since the upper electrode and theupper-electrode lead electrode are formed in different processes, thethickness of the upper electrode can be reduced easily. Further, as aresult of decreasing the thickness of the upper electrode, the amount ofdisplacement of the piezoelectric layer increases.

A seventeenth aspect of the present invention is the liquid-jet headaccording to any one of the first to sixteenth aspects, wherein thepiezoelectric layer and the upper electrode of each piezoelectricelement extend to the outside of a region facing the correspondingpressure generation chamber so that a piezoelectric non-active portionis formed, and an end portion of the upper-electrode lead electrode onthe side toward the upper electrode is located on the piezoelectricnon-active portion and outside the pressure generation chamber.

In the seventeenth aspect, it is possible to prevent generation ofcracks or the like in the piezoelectric element, which would otherwisebe generated when the piezoelectric element is driven, because ofgeneration of noncontiguous stress in a region facing the end portion ofthe pressure generation chamber.

An eighteenth aspect of the present invention is the liquid-jet headaccording to any one of the first to seventeenth aspects, wherein in astate in which the connection wiring is connected, the connectionportions are covered with a sealing material formed of an organicinsulating material.

In the eighteenth aspect, since permeation of water from the exposedportions is prevented, breakage of the piezoelectric layer can morereliably prevented.

A nineteenth aspect of the present invention is the liquid-jet headaccording to any one of the fourteenth to eighteenth aspects, whereinthe insulating film includes a first insulating film and a secondinsulating film, the piezoelectric elements are covered by the firstinsulating film except for the connection portion for connection withthe upper-electrode lead electrode, the upper-electrode lead electrodeis provided on the first insulating film, and at least the patternregions of the respective layers which constitute the piezoelectricelements and the upper-electrode lead electrode are covered with thesecond insulating film except for regions facing the connectionportions.

In the nineteenth aspect, since permeation of water to the piezoelectriclayer is reliably prevented by the first and second insulating films,deterioration (breakage) of the piezoelectric layer (piezoelectricelements) due to water (moisture) can be reliably prevented over a longperiod of time.

A twentieth aspect of the present invention is the liquid-jet headaccording to any one of the fourteenth to nineteenth aspects, whereinthe connection wiring includes a second upper-electrode lead electrodeextending from the upper-electrode lead electrode, the secondupper-electrode lead electrode is provided on the insulating film and isconnected to the upper-electrode lead electrode at the connectionportion, and a terminal portion to which drive wring is connected isprovided at a tip end portion of the second upper-electrode leadelectrode.

In the twentieth aspect, since the piezoelectric layer is covered withthe insulating film formed of an inorganic insulating material having alow water permeability, and the insulating film is continuously providedto enter under the terminal portion. Therefore, even when water(moisture) enters under the insulating film, water is more reliablyprevented from coming into contact with the piezoelectric layer.Accordingly, deterioration (breakage) of the piezoelectric layer(piezoelectric elements) due to water (moisture) can be reliablyprevented over a long period of time.

A twenty-first aspect of the present invention is the liquid-jet headaccording to any one of the fourteenth to twentieth aspect, wherein thepiezoelectric layer and the upper electrode of each piezoelectricelement extend to the outside of a region facing the correspondingpressure generation chamber so that a piezoelectric non-active portionis formed, and an upper-electrode-side end portion of theupper-electrode lead electrode which is connected to the upper electrodeis located on the piezoelectric non-active portion and outside thepressure generation chamber.

In the twenty-first aspect, it is possible to prevent generation ofcracks or the like in the piezoelectric element, which would otherwisebe generated when the piezoelectric element is driven, because ofgeneration of noncontiguous stress in a region facing the end portion ofthe pressure generation chamber.

A twenty-second aspect of the present invention is the liquid-jet headaccording to any one of the fourteenth to twenty-first aspects, whereina protective plate having a piezoelectric-element-holding portion, whichis a space for protecting the piezoelectric elements, is bonded to asurface of the channel substrate, the surface being located on the sidetoward the piezoelectric elements, and the connection portion of theupper-electrode lead electrode is provided outside thepiezoelectric-element-holding portion.

In the twenty-second aspect, since the protective plate is bonded to theinsulating film in a state in which the connection portion is providedoutside the piezoelectric-element-holding portion, the bonding strengthof the protective plate increases.

A twenty-third aspect of the present invention is the liquid-jet headaccording to any one of the first to twenty-second aspects, wherein aprotective plate having a piezoelectric-element-holding portion, whichis a space for protecting the piezoelectric elements, is bonded to asurface of the channel substrate, the surface being located on the sidetoward the piezoelectric elements, the protective plate includes a flowpassage for liquid to be supplied to the pressure generation chambers,the adhesive layer located on the flow passage side of thepiezoelectric-element-holding portion is exposed to the interior of theflow passage, and a moisture permeable portion which enables permeationof water within the piezoelectric-element-holding portion is provided ina region located other than the flow passage side of thepiezoelectric-element-holding portion.

In the twenty-third aspect, since water (moisture) having permeated fromthe flow passage to the piezoelectric-element-holding portion via theadhesive layer is discharged to the outside via the moisture permeableportion, the humidity within the piezoelectric-element-holding portionis maintained at least at a level close to the humidity of the outsideair. Since the piezoelectric elements are covered with the insulatingfilm, if the humidity within the piezoelectric-element-holding portionis maintained at a level close to the humidity of outside air, breakageof the piezoelectric elements due to water (moisture) can be prevented.

A twenty-fourth aspect of the present invention is the liquid-jet headaccording to the twenty-third aspect, wherein the moisture permeableportion is formed of an organic material.

In the twenty-fourth aspect, since the moisture permeable portion isformed of an organic material, which is a material having a high waterpermeability, water within the piezoelectric-element-holding portion canbe effectively discharged.

A twenty-fifth aspect of the present invention is the liquid-jet headaccording to the twenty-third or twenty-fourth aspects, wherein themoisture permeable portion is provided on a portion of a bonding surfaceof the protective plate, the bonding surface being bonded to the channelsubstrate.

In the twenty-fifth aspect, the moisture permeable portion can be formedin a relatively easy manner.

A twenty-sixth aspect of the present invention is the liquid-jet headaccording to the twenty-third or twenty-fourth aspects, wherein themoisture permeable portion is provided on an upper surface of theprotective plate.

In the twenty-sixth aspect, the moisture permeable portion can be formedin a relatively easy manner.

A twenty-seventh aspect of the present invention is the liquid-jet headaccording to the twenty-fifth or twenty-sixth aspects, wherein themoisture permeable portion is formed of an adhesive having a waterpermeability higher than that of an adhesive which constitutes theadhesive layer.

In the twenty-seventh aspect, since the channel substrate and theprotective plate are bonded together by the adhesive layer and themoisture permeable portion, the bonding strength increases.

A twenty-eighth aspect of the present invention is the liquid-jet headaccording to any one of the twenty-third to twenty-sixth aspects,wherein the moisture permeable portion is formed of a potting material.

In the twenty-eighth aspect, the moisture permeable portion can beeasily formed, and the moisture permeable has a high water permeability.

A twenty-ninth aspect of the present invention is the liquid-jet headaccording to any one of the twenty-third to twenty-eighth aspect,wherein the moisture permeable portion is provided in a region on a sideof the piezoelectric-element-holding portion opposite the flow passage.

In the twenty-ninth aspect, water within the flow passage does notpermeate via the moisture permeable portion, and water within thepiezoelectric-element-holding portion is discharged effectively via themoisture permeable portion.

A thirtieth aspect of the present invention is the liquid-jet headaccording to the twenty-third or twenty-fourth aspects, wherein themoisture permeable portion is provided on the protective plate in eachof the regions outside the opposite ends of the row of pressuregeneration chambers.

In the thirtieth aspect, breakage of the piezoelectric elements due towater can be prevented over a long period of time.

A thirty-first aspect of the present invention is a liquid-jet apparatuscharacterized by comprising the liquid-jet head according to any one ofthe first to thirtieth aspects.

In the thirty-first aspect, a liquid-jet apparatus having improveddurability and reliability is realized.

A thirty-second aspect of the present invention is a method ofmanufacturing a liquid-jet head, comprising the steps of formingpiezoelectric elements, each of which is composed of a lower electrode,a piezoelectric layer, and an upper electrode, on one surface of achannel substrate via a vibration plate, the channel substrate havingpressure generation chambers formed therein and communicating nozzleorifices for discharging liquid droplets; forming an upper-electrodelead electrode extending from the upper electrode of each piezoelectricelement; forming an insulating film of an inorganic insulating materialover the entirety of a surface of the channel substrate, the surfacefacing the piezoelectric elements; and patterning the insulating filmsuch that at least connection-wiring connection portions of the lowerelectrode and the upper-electrode lead electrode are exposed, and theinsulating film is left in pattern regions of the respective layers ofthe piezoelectric elements and the upper-electrode lead electrode,except for the connection portion.

In the thirty-second aspect, the insulating film can be formed properlywithin the pattern regions of the piezoelectric elements and theupper-electrode lead electrode, except for the connection portion.

A thirty-third aspect of the present invention is the method ofmanufacturing a liquid-jet head according to the thirty-second aspect,wherein in the step of patterning the insulating film, a portion of theinsulating film within a predetermined region is removed by means of ionmilling.

In the thirty-third aspect, the insulating film can be removed well withhigh dimensional accuracy.

A thirty-fourth aspect of the present invention is the method ofmanufacturing a liquid-jet head according to the thirty-second orthirty-third aspect, wherein the method includes, after the step ofpatterning the insulating film, a step of bonding a protective plate toa surface of the channel substrate, the surface facing the piezoelectricelements, the protective plate including a piezoelectric-element-holdingportion for protecting the piezoelectric elements and a flow passage forliquid to be supplied to the pressure generation chambers, wherein inthe step of bonding the protective plate, an adhesive is applied to theprotective plate such that a space portion is left in a portion of aregion surrounding the piezoelectric-element-holding portion, except fora region located on the side toward the flow passage, the protectiveplate is bonded to the channel substrate, and the space portion issealed by a material having a water permeability higher than that of theadhesive so as to form a moisture permeable portion through which waterwithin the piezoelectric-element-holding portion permeates.

In the thirty-fourth aspect, the moisture permeable portion can beeasily formed without making the production process complicated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a recording head according toEmbodiment 1.

FIGS. 2A-2B show plan and sectional views of the recording headaccording to Embodiment 1.

FIGS. 3A-3B show plan and sectional views of a main portion of therecording head according to Embodiment 1.

FIG. 4 is a plan view showing a modification of the recording headaccording to Embodiment 1.

FIGS. 5A-5D are sets of sectional views showing steps of manufacturingthe recording head according to Embodiment 1.

FIGS. 6A-6D are sets of sectional views showing steps of manufacturingthe recording head according to Embodiment 1.

FIG. 7 is a schematic perspective view of a recording head according toEmbodiment 2.

FIGS. 8A-8B show plan and sectional views of the recording headaccording to Embodiment 2.

FIG. 9 is a plan view showing a main portion of the recording headaccording to Embodiment 2.

FIGS. 10A-10B are pairs of sectional views showing the main portion ofthe recording head according to Embodiment 2.

FIGS. 11A-11D are sets of sectional views showing steps of manufacturingthe recording head according to Embodiment 2.

FIG. 12 is a schematic perspective view of a recording head according toEmbodiment 3.

FIGS. 13A-13B show plan and sectional views of the recording headaccording to Embodiment 3.

FIG. 14 is a plan view showing a main portion of the recording headaccording to Embodiment 3.

FIG. 15 is a plan view showing a modification of the recording headaccording to Embodiment 3.

FIGS. 16A-16D are sets of sectional views showing steps of manufacturingthe recording head according to Embodiment 3.

FIGS. 17A-17C are sets of sectional views showing steps of manufacturingthe recording head according to Embodiment 3.

FIGS. 18A-18B show plan and sectional views of the recording headaccording to Embodiment 4.

FIG. 19 is a schematic perspective view of a recording head according toEmbodiment 5.

FIGS. 20A-20B show plan and sectional views of the recording headaccording to Embodiment 5.

FIGS. 21A-21D are sets of sectional views showing steps of manufacturingthe recording head according to Embodiment 5.

FIG. 22 is a side view of a recording head according to Embodiment 6.

FIG. 23 is a schematic view of a recording apparatus according to oneembodiment.

DESCRIPTION OF REFERENCE NUMERALS

10 channel substrate; 12 pressure generation chamber; 20 nozzle plate;21 nozzle orifice; 30 protective plate; 31 piezoelectric-element-holdingportion; 32 reservoir section; 33 through-hole; 35 adhesive; 40compliance substrate; 50 elastic film; 55 insulating film; 60 lowerelectrode film; 70 piezoelectric layer; 80 upper electrode film; 90, 90Alead electrodes for upper electrodes; 90 a connection portion; 100insulating film; 110 reservoir; 120 drive IC; 130 connection wiring; 140sealing material; 300 piezoelectric element; 330 piezoelectricnon-active portion

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will next be described in detail by way ofembodiments.

EMBODIMENT 1

FIG. 1 is an exploded perspective view of an ink-jet recording headaccording to Embodiment 1 of the present invention. FIG. 2 shows planand sectional views of the recording head of FIG. 1. As shown in thesedrawings, in the present embodiment a channel substrate 10 is formed ofa monocrystalline silicon substrate which has a crystal face orientationof (110). An elastic film 50 is formed beforehand on one side of thechannel substrate 10 by means of thermal oxidation. The elastic film 50is formed of silicon dioxide and has a thickness of 0.5 μm to 2 μm. Inthe channel substrate 10, a plurality of pressure generation chambers 12are provided in proximity, in a row arrangement in their widthdirection. A communication section 13 is formed in the channel substrate10 in a region located longitudinally outside the pressure generationchambers 12. The communication section 13 communicates with the pressuregeneration chambers 12 via corresponding ink supply channels 14 providedfor the pressure generation chambers 12. The communication section 13communicates with a reservoir section of a protective plate, which willbe described later, and partially constitutes a reservoir, which servesas a common ink chamber for the pressure generation chambers 12. The inksupply channels 14 are formed narrower than the pressure generationchambers 12 so as to maintain constant flow resistance of ink flowinginto the pressure generation chambers 12 from the communication section13.

A nozzle plate 20 is bonded to the orifice side of the channel substrate10, by use of adhesive, a thermally fusing film, or the like, via aninsulating film 51 having been used as a mask for formation of thepressure generation chambers 12. Nozzle orifices 21 are formed throughthe nozzle plate 20 and communicate with the corresponding pressuregeneration chambers 12 at end portions opposite the ink supply channels14. Notably, the nozzle plate 20 has a thickness of, for example, 0.01mm to 1 mm, and is made of a suitable material, such as glass ceramic,monocrystalline silicon substrate, or stainless steel, which has acoefficient of linear expansion of, for example, 2.5 to 4.5×10⁻⁶/° C. at300° C. or less.

As described above, the elastic film 50 having a thickness of, forexample, about 1.0 μm is formed on a side of the channel substrate 10opposite the orifice side. An insulating film 55 having a thickness of,for example, about 0.4 μm is formed on the elastic film 50. A lowerelectrode film 60 having a thickness of, for example, about 0.2 μm, apiezoelectric layer 70 having a thickness of, for example, about 1.0 μm,and an upper electrode film 80 having a thickness of, for example, about0.05 μm are formed in layers on the insulating film 55 by a process tobe described later, thereby forming a piezoelectric element 300. Herein,the piezoelectric element 300 refers to a section that includes thelower electrode film 60, the piezoelectric layer 70, and the upperelectrode film 80. Generally, either the lower electrode or the upperelectrode of the piezoelectric element 300 assumes the form of a commonelectrode for use among the piezoelectric elements 300, whereas theother electrode and the piezoelectric layer 70 are formed, throughpatterning, for each of the pressure generation chambers 12. The otherelectrode and the piezoelectric layer 70 formed through patterningconstitute a piezoelectric active portion, which produces apiezoelectric strain when voltage is applied between the upper and lowerelectrodes. According to the present embodiment, the lower electrodefilm 60 serves as a common electrode for use among the piezoelectricelements 300, whereas the upper electrode film 80 serves as anindividual electrode for use with a piezoelectric element 300. However,the configuration may be reversed in accordance with needs of a drivecircuit and wiring. In either case, piezoelectric active portions areformed individually for corresponding pressure generation chambers.Herein, a piezoelectric element 300 and the vibration plate, which isdisplaced through activation of the piezoelectric element 300,constitute a piezoelectric actuator.

In the present embodiment, as shown in FIGS. 2 and 3, the lowerelectrode film 60 is formed in a region facing the pressure generationchambers 12 with respect to the longitudinal direction of the pressuregeneration chambers 12 and extends continuously through respectiveregions corresponding to the plurality of pressure generation chambers12. Further, at a location outside the row of the pressure generationchambers 12 and at a location between the piezoelectric elements 300,the lower electrode film 60 extends to the vicinity of the communicationsection 13. The end portions of these extensions serve as connectionportions 60 a, to which drive wiring 130 to be described later isconnected. The piezoelectric layer 70 and the upper electrode layer 80are basically provided within a region facing each pressure generationchamber 12. However, with respect to the longitudinal direction of thepressure generation chamber 12, they extend to a point outside the endportion of the lower electrode film 60, and the end surface of the lowerelectrode film 60 is covered with the piezoelectric layer 70. Apiezoelectric non-active portion 330, which includes a piezoelectriclayer but is not substantially driven, is formed in the vicinity of thelongitudinal end of each pressure generation chamber 12. A leadelectrode 90 for the upper electrode is connected to one end of theupper electrode film 80. In the present embodiment, the upper-electrodelead electrode 90 extends from a point on the piezoelectric non-activeportion 330 located outside the pressure generation chamber 12 to thevicinity of the communication section 13, and the end portion of theextension serves as a connection portion 90 a to which the drive wiring130 is connected, as in the case of the lower electrode film 60.

In the present invention, at least pattern regions of the respectivelayers that constitute the piezoelectric elements 300 are covered withan insulating film 100 formed of an inorganic insulating material. Inthe present embodiment, the pattern regions of the respective layersthat constitute the piezoelectric elements 300 and a pattern region ofthe upper-electrode lead electrodes 90 are covered with the insulatingfilm 100, except for regions facing the connection portions 60 a of thelower electrode film 60 and the connection portions 90 a of theupper-electrode lead electrodes 90. That is, the surfaces (uppersurfaces and end surfaces) of the lower electrode film 60, thepiezoelectric layers 70, the upper electrode films 80, and theupper-electrode lead electrodes 90 in the pattern regions are coveredwith the insulating film 100 formed of an inorganic insulating material.

Since the insulating film 100 formed of an inorganic insulating materialhas very low permeability against water even when its thickness issmall, breakage of the piezoelectric layers 70 due to water (moisture)can be prevented by means of covering the surfaces of at least thesurfaces of the lower electrode film 60, the piezoelectric layers 70,and the upper electrode films 80 with the insulating film 100, and, inthe present embodiment, further covering the surfaces of theupper-electrode lead electrodes 90 with the insulating film 100. Sincethe surfaces of the respective layers that constitute the piezoelectricelements 300 and the upper-electrode lead electrodes 90 are covered withthe insulating film 100, except for the connection portions 60 a and 90a, even when water enters through a clearance between these layers andthe insulating film 100, water can be prevented from reaching thepiezoelectric layers 70, whereby breakage of the piezoelectric layers 70due to water can be prevented more reliably.

No limitation is imposed on the material of the insulating film 100,insofar as the material is an inorganic insulating material. Examples ofsuch an inorganic insulating material include aluminum oxide (AlO_(X))and tantalum oxide (TaO_(X)). In particular, use of aluminum oxide(Al₂O₃), which is an inorganic amorphous material, is preferred.

When the insulating film 100 is formed of aluminum oxide, the insulatingfilm 100 preferably has a thickness of about 30 to 150 nm, morepreferably about 100 nm. In the case where aluminum oxide is used as amaterial for the insulating film 100, even when the insulating film 100is formed to have a thickness as thin as 100 nm, permeation of waterunder a high humidity environment can be prevented sufficiently.Notably, in the case where an organic insulating material such as resinis used as a material for the insulating film, permeation of watercannot be prevented sufficiently if the insulating film has a smallthickness similar to that of the above-described insulating film formedof the inorganic insulating material. Further, increasing the thicknessof the insulating film so as to prevent permeation of water may hinderdisplacement of the piezoelectric elements.

The insulating film 100 formed of aluminum oxide preferably has a filmdensity of 3.08 to 3.25 g/cm³. Further, the insulating film 100preferably has a Young's modulus of elasticity of 170 to 200 GPa.Covering the piezoelectric elements 300, etc. with the insulating film100 having such properties prevents permeation of water under ahigh-humidity environment more reliably, without hindering displacementof the piezoelectric elements 300. Notably, the insulating film 100 isformed by CVD or any other suitable process. The insulating film 100having desired properties, such as film density and Young's modulus ofelasticity, can be formed relatively easily through adjustment ofvarious conditions, such as temperature and gas flow rate, under whichthe insulating film 100 is formed.

The sum of stress of the insulating film 100 and stress of the upperelectrode film 80; i.e., the sum of stress of the upper electrode film80 and that of the insulating film 100 formed on the upper electrodefilm 80, is preferably compressive stress. The stress of the insulatingfilm 100 and the stress of the upper electrode film 80 refer to internalstresses (film stresses) generated within the respective films, and thestress σ of the upper electrode film 80 and that of the insulating film100 are each represented by the product of Young's modulus of elasticityY, distortion ε, and film thickness m; i.e., ε×Y×m.

The internal stresses of the piezoelectric elements 300 located inregions facing the pressure generation chambers 12 change upon formationof the pressure generation chambers 12 during a manufacturing process,which will be described later. Specifically, during formation of thepressure generation chambers 12 under the piezoelectric elements 300after formation of the piezoelectric elements 300, the internal stressof the piezoelectric layer 70 in the tensile direction is relaxed, and aforce is generated in a direction (compressive direction) such that thevibration plate deforms toward the pressure generation chambers.However, in the present embodiment, the piezoelectric elements 300 arecovered with the insulating film 100 formed of an inorganic insulatingmaterial, and the sum of stress of the insulating film 100 and stress ofthe upper electrode film 80 is compressive stress. Therefore, afterformation of the pressure generation chambers 12, stresses (compressivestresses) of the insulating film 100 and the upper electrode film 80 arereleased, so that a force in the tensile direction acts on thepiezoelectric elements 300 (the piezoelectric layer 70). Thiseffectively prevents a decrease in amount of displacement of thevibration plate caused through drive of the piezoelectric elements 300,while reliably preventing breakage of the piezoelectric layer 70 underinfluence of the external environment such as water.

Both the stress of the insulating film 100 and the stress of the upperelectrode film 80 may be compressive. Alternatively, the stress of theinsulating film 100 may be compressive and the stress of the upperelectrode film 80 tensile. In this case, the stress σ₁ of the upperelectrode film 80 and the stress σ₂ of the insulating film 100 satisfythe relation |σ₁|<|σ₂|.

In the present embodiment, the end portions of extensions of the lowerelectrode film 60 extending to the vicinity of the communication section13 serve as the connection portions 60 a for connection with the drivewring 130. However, this configuration may be modified as shown in FIG.4. That is, the lower-electrode lead electrodes 95, which areelectrically connected to the lower electrode film 60 and locatedoutside the row of the piezoelectric elements 300 and between thepiezoelectric elements 300, extend to the vicinity of the communicationsection 13, and the end portions of the lower-electrode lead electrodes95 serve as the connection portions 95 a for connection with the drivewring 130. In this case, the pattern region, except for the connectionportions 90 a of the upper-electrode lead electrodes 90 and theconnection portions 95 a of the lower-electrode lead electrode 95, iscovered with the insulating film 100 formed of an inorganic insulatingmaterial.

Further, a protective plate 30 is bonded to the channel substrate 10 onthe side toward the piezoelectric elements 300, via adhesive 35. Theprotective plate 30 has a piezoelectric-element-holding portion 31 in aregion facing the piezoelectric elements 300 so as to secure a space ofa size which does not hinder movements of the piezoelectric elements300. Since the piezoelectric elements 300 are formed within thepiezoelectric-element-holding portion 31, the piezoelectric elements 300are protected and hardly influenced by the external environment.Moreover, a reservoir section 32 is formed in the protective plate 30 ina region corresponding to the communication section 13 of the channelsubstrate 10. In the present embodiment, this reservoir section 32penetrates the protective plate 30 in the thickness direction andextends along the row of the pressure generation chambers 12. Asdescribed above, the reservoir section 32 communicates with thecommunication section 13 of the channel substrate 10 to therebyconstitute a reservoir 110, which serves as a common ink chamber for thepressure generation chambers 12.

Further, in a region of the protective plate 30 between thepiezoelectric-element-holding portion 31 and the reservoir section 32, athrough-hole 33 penetrates the protective plate 30 in the thicknessdirection. The above-described connection portions 60 a of the lowerelectrode film 60 and the above-described connection portions 90 a ofthe upper-electrode lead electrodes 90 are exposed within thethrough-hole 33. The drive wiring 130, which serves as connection wiringfor establishing electrical connection between a drive IC 120 mounted onthe protective plate 30 and the piezoelectric elements 300, is connectedto the connection portions 60 a of the lower electrode film 60 and theconnection portions 90 a of the upper-electrode lead electrodes 90. Inthe present embodiment, the drive wiring 130 is formed of bonding wires,and is caused to extend into the through-hole 33 so as to electricallyconnect the drive IC 120 to the connection portions 60 a of the lowerelectrode film 60 and the connection portions 90 a of theupper-electrode lead electrodes 90. Notably, the through-hole 33,through which the drive wiring 130 extends, is filled with a sealingmaterial 140, which is an organic insulating material (in the presentembodiment, potting material). Thus, the connection portions 60 a of thelower electrode film 60, the connection portions 90 a of theupper-electrode lead electrodes 90, and the drive wiring 130 arecompletely covered with the sealing material 140.

Examples of the material of the protective plate 30 include glass,ceramic, metal, and resin. However, the protective plate 30 ispreferably formed of a material having a coefficient of thermalexpansion approximately equal to that of the channel substrate 10. Inthe present embodiment, the protective plate 30 is formed of amonocrystalline silicon substrate, which is the same material as thatused for the channel substrate 10.

A compliance substrate 40 is bonded onto the protective plate 30. Thecompliance substrate 40 includes a sealing film 41 and a fixing plate42. The sealing film 41 is formed of a flexible material having lowrigidity (e.g., polyphenylene sulfide (PPS) having a thickness of 6 μm).One end surface of the reservoir section 32 is sealed by means of thesealing film 41. The fixing plate 42 is formed of a hard, rigidmaterial, such as metal (e.g., stainless steel (SUS) having a thicknessof 30 μm). A region of the fixing plate 42 that faces the reservoir 110is completely removed in the thickness direction of the fixing plate 42,thereby forming an opening portion 43. As a result, one side of thereservoir 110 is sealed merely with the sealing film 41 havingflexibility.

The thus-configured ink-jet recording head of the present embodimentoperates in the following manner. Unillustrated external ink supplymeans supplies ink to the ink-jet recording head. The thus-supplied inkfills an internal space extending from the reservoir 110 to the nozzleorifices 21. Subsequently, in accordance with a record signal from thedrive IC 120, voltage is applied between the lower electrode film 60 andthe upper electrode film 80 corresponding to each of the pressuregeneration chambers 12, thereby causing the elastic film 50, theinsulating film 55, the lower electrode film 60, and the piezoelectriclayer 70 to be deformed in a deflected manner. As a result, pressurewithin the pressure generation chambers 12 increases, thereby causingink droplets to be discharged from the corresponding nozzle orifices 21.

A method for manufacturing such an ink-jet recording head will bedescribed with reference to FIGS. 5 and 6. Notably, FIGS. 5 and 6 aresectional views taken along the longitudinal direction of the pressuregeneration chambers 12. First, as shown in FIG. 5( a), the channelsubstrate 10, which is a monocrystalline silicon substrate, is thermallyoxidized at about 1100° C. in a diffusion furnace, thereby formingsilicon dioxide films 52, which serve as the elastic film 50 and a maskfilm 51, on the surface of the channel substrate 10. Next, as shown inFIG. 5( b), after a zirconium (Zr) layer is formed on the elastic film50 (silicon dioxide film 52), the channel substrate 10 is thermallyoxidized at, for example, 500° C. to 1,200° C. in the diffusion furnace,thereby forming the insulating film 55, which is formed of zirconiumoxide (ZrO₂). Next, as shown in FIG. 5( c), the lower electrode film 60is formed on the insulating film 55 by use of platinum and iridium.Subsequently, the lower electrode film 60 is patterned to apredetermined shape.

Next, as shown in FIG. 5( d), the piezoelectric layer 70 formed of, forexample, lead zirconate titanate (PZT) and the upper electrode film 80formed of, for example, iridium are formed over the entire surface ofthe channel substrate 10. Subsequently, as shown in FIG. 6( a), thepiezoelectric layer 70 and the upper electrode film 80 are patterned tocorrespond to the pressure generation chambers 12, to thereby form thepiezoelectric elements 300.

Notably, in place of ferroelectric piezoelectric materials such as leadzirconate titanate (PZT), the piezoelectric layer 70, which constitutesthe piezoelectric element 300, can be formed by use of relaxorferroelectric material which is obtained by adding, to a ferroelectricpiezoelectric material, a metal such as niobium, nickel, magnesium,bismuth, or yttrium. Although its composition may be freely selected inconsideration of the characteristics, application, etc. of thepiezoelectric elements 300, examples of the composition includePbTiO₃(PT), PbZrO₃(PZ), Pb(Zr_(X)Ti_(1−X)) O₃ (PZT),Pb(Mg_(1/3)Nb_(2/3))O₃—PbTiO₃(PMN—PT),Pb(Zn_(1/3)Nb_(2/3))O₃—PbTiO₃(PZN—PT),Pb(Ni_(1/3)Nb_(2/3))O₃—PbTiO₃(PNN—PT), Pb(In_(1/2)Nb_(1/2))O₃—PbTiO₃(PIN—PT),Pb(Sc_(1/3)Ta_(1/2))O₃—PbTiO₃(PST-PT),Pb(Sc_(1/3)Nb_(1/2))O₃—PbTiO₃(PSN—PT), BiScO₃—PbTiO₃(BS—PT), andBiYbO₃—PbTiO₃(BY—PT).

Next, the upper-electrode lead electrodes 90 are formed. Specifically,as shown in FIG. 6( b), a close contact layer 91 formed of, for example,titanium tungsten (TiW) is formed over the entire surface of the channelsubstrate 10, and a metal layer 92 formed of, for example, gold (Au) isformed over the entire surface of the close contact layer 91. Afterthat, the metal layer 92 is patterned for each piezoelectric element 300via a mask pattern (not shown) formed of resist or the like, and theclose contact layer 91 is patterned through etching, whereby theupper-electrode lead electrodes 90 are formed. Notably, the closecontact layer 91 is preferably etched in such a manner that its endsurface is located to coincide with the end surface of the metal layer92 or located outside the end surface of the metal layer 92.

Next, as shown in FIG. 6( c), the insulating film 100 of aluminum oxide(Al₂O₃) is formed, and is then patterned to a predetermined shape.Specifically, the insulating film 100 is formed over the entire surfaceof the channel substrate 10. Subsequently, the insulating film 100 isremoved from regions corresponding to the connection portions 60 a ofthe lower electrode film 60 and the connection portions 90 a of theupper-electrode lead electrodes 90. Notably, in the present embodiment,the insulating film 100 is removed from regions corresponding to theconnection portions 60 a and 90 a, and from the remaining region exceptfor the pattern regions of the constituting layers of the piezoelectricelements 300 and the upper-electrode lead electrodes 90. Needless tosay, the insulating film 100 may be removed from only the regionscorresponding to the connection portions 60 a and 90 a. In either case,the essential requirement is that the insulating film 100 covers thepattern regions of the layers of the piezoelectric elements 300 and theupper-electrode lead electrodes 90, except for the connection portions60 a of the lower electrode film 60 and the connection portions 90 a ofthe upper-electrode lead electrodes 90. No limitation is imposed on themethod of removing the insulating film 100. However, use of dry etchingsuch as ion milling is preferred. This enables proper removal of theinsulating film 100 with high dimensional accuracy.

Next, as shown in FIG. 6( d), the protective plate 30 is bonded to thechannel substrate 10 on the side toward the piezoelectric elements 300by use of the adhesive 35. Subsequently, via the mask film 51 patternedto a predetermined shape, the channel substrate 10 is anisotropicallyetched so as to form the pressure generation chambers 12, etc. Then, theelastic film 50 and the insulating film 55 are mechanically removed soas to establish communication between the communication section 13 andthe reservoir section 32.

In actual practice, a large number of chips are simultaneously formed ona single wafer by means of a series of film formation steps as describedabove and anisotropic etching. Subsequently, the wafer is diced intochips each corresponding to the channel substrate 10 shown in FIG. 1.Subsequently, the nozzle plate 20 is bonded to the channel substrate 10via the mask film 51, a drive IC 120 is mounted to the protective plate30, and the compliance substrate 40 is bonded to the protective plate30. Further, through wire bonding, the drive wiring 130 is formedbetween the drive IC 120, and the connection portions 60 a of the lowerelectrode film 60 and the connection portions 90 a of theupper-electrode lead electrodes 90. The connection portions 60 a and 90a and the drive wiring 130 are covered with the sealing material 140,whereby an ink-jet recording head according to the present embodiment iscompleted.

TEST EXAMPLE 1

Ink-jet recording heads of Examples 1 to 3 and Comparative Examples 1 to3 as described below were fabricated, and tested under application of DCthereto. The test conditions and test results are shown below in Table1.

EXAMPLE 1

An ink-jet recording head of Example 1 was manufactured in such a mannerthat an insulating film of aluminum oxide, which is an inorganicinsulating material, was formed to have a thickness of about 50 nm andto cover the pattern regions of the respective layers of thepiezoelectric elements and the upper-electrode lead electrodes, exceptfor the connection portions of the lower electrode film and theconnection portions of the upper-electrode lead electrodes.

EXAMPLE 2

An ink-jet recording head of Example 2 was manufactured to have the samestructure as that of Example 1, except that the insulating film wasformed to have a thickness of about 100 nm.

EXAMPLE 3

An ink-jet recording head of Example 3 was manufactured to have the samestructure as that of Example 1, except that in place of aluminum oxide,tantalum oxide was used to form the insulating film, and the insulatingfilm had a thickness of about 200 nm.

COMPARATIVE EXAMPLE 1

An ink-jet recording head of Comparative Example 1 was manufactured tohave the same structure as that of Example 1, except that silicone oil(product of Daikin Industries, Ltd.) was used to form the insulatingfilm so as to completely cover the surfaces of the piezoelectricelements and the upper-electrode lead electrodes, except for theconnection portions of the lower electrode film and the connectionportions of the upper-electrode lead electrodes.

COMPARATIVE EXAMPLE 2

An ink-jet recording head of Comparative Example 2 was manufactured tohave the same structure as that of Comparative Example 1, except thaturethane-containing damp-proofing agent (product of Hitachi ChemicalCo., Ltd.) was used to form the insulating film.

COMPARATIVE EXAMPLE 3

An ink-jet recording head of Comparative Example 3 was manufactured tohave the same structure as that of Example 1, except that the insulatingfilm was not formed.

TABLE 1 Tested Number Applied Evaluation Number of of NG voltage Temp.Humidity time segments segments Yield Example 1 35 V 25° C. 40% Rh 250 H48 0 100% Example 2 35 V 25° C. 85% Rh 250 H 47 0 100% Example 3 35 V25° C. 40% Rh 150 H 50 0 100% Comparative 35 V 25° C. 40% Rh  4 H 25 18 28% Example 1 Comparative 35 V 25° C. 40% Rh  4 H 30 2  93% Example 2Comparative 35 V 25° C. 40% Rh  4 H 25 4  84% Example 3

As shown in Table 1, in the ink-jet recording heads of Examples 1 to 3each having an insulating film of an inorganic insulating material, nosegment (piezoelectric element) was broken even after passage of 150hours or more under an environment of 40% relative humidity, and theiryields were 100%. In particular, in the ink-jet recording head ofExample 2 in which aluminum oxide was used, no segment (piezoelectricelement) was broken even after passage of 250 hours, despite theconsiderably severe condition of 85% relative humidity. In contrast, inthe ink-jet recording heads of Comparative Examples 1 to 3, each havingan insulating film of a material other than inorganic insulatingmaterials or having no insulating film, a portion of the segments wasobserved to be broken after passage of four hours under an environmentof 40% relative humidity. The test revealed that in the ink-jetrecording head of the comparative examples, permeation of water occursmore easily as compared with the ink-jet recording head in which theabove-described insulating film formed of an inorganic insulatingmaterial is provided.

When an insulating film formed of a material other than an inorganicinsulating material is used, permeation of water cannot be prevented toa sufficient degree if the insulating film has a small thickness as inthe case of the insulating film formed of an inorganic insulatingmaterial. Further, when the thickness of the insulating film isincreased so as to prevent permeation of water, the insulating film mayhinder the drive of the piezoelectric elements 300. Therefore, in orderto secure a sufficient level of drive of the piezoelectric elements 300,the piezoelectric elements 300 are required to have a larger size, sothat the size of the ink-jet recording head increases.

As is apparent from the results, the structure according to the presentinvention can reliably prevent breakage of piezoelectric elements due tomoisture (water), without increasing the size of the head, to therebygreatly improve the durability of the head.

TEST EXAMPLE 2

Ink-jet recording heads of Examples 4 to 6 and Comparative Example 4 asdescribed below were fabricated, and tested so as to compare the amountsof displacement of their vibration plates. Table 2 provided below showthe materials, thicknesses, and film stresses of the upper electrodefilm and the insulating film of each of the ink-jet recording heads ofExamples 4 to 6 and Comparative Example 4. Table 3 provided below showdata regarding physical properties (Young's modulus and stress) ofmaterials of the upper electrode film and the insulating film. Notably,in Tables 2 and 3, compressive stress is shown as a negative value, andtensile stress is shown as a positive value.

EXAMPLE 4

An ink-jet recording head of Example 4 was manufactured in such a mannerthat, as shown in Table 2, an upper electrode film having a thickness ofabout 50 nm was formed from iridium, and an insulating film having athickness of about 100 nm was formed from aluminum oxide so as to coverthe piezoelectric elements having the upper electrode film.

As shown in Tables 2 and 3, a film formed of iridium producescompressive stress, and a film formed of aluminum oxide producescompressive stress. Therefore, in the ink-jet recording head of Example4, compressive stress is produced in each of the upper electrode filmand the insulating film, and the sum of the stresses produced in theupper electrode film and the insulating film is compressive.

EXAMPLE 5

An ink-jet recording head of Example 5 was manufactured to have the samestructure as that of Example 4, except that platinum was used as thematerial for the upper electrode film.

As shown in Tables 2 and 3, a film formed of platinum produces tensilestress, and a film formed of aluminum oxide produces compressive stress.Therefore, in the ink-jet recording head of Example 5, compressivestress is produced in the insulating film, and tensile stress isproduced in the upper electrode film. However, since the stress σ₁ ofthe upper electrode film and the stress σ₂ of the insulating filmsatisfy the relation |σ₁|<|σ₂|, the sum of the stresses produced in theupper electrode film and the insulating film is compressive.

EXAMPLE 6

An ink-jet recording head of Example 6 was manufactured to have the samestructure as that of Example 5, except that the upper electrode film wasformed to have a thickness of about 100 nm.

In the ink-jet recording head of Example 6, as in the case of Example 5,compressive stress is produced in the insulating film, and tensilestress is produced in the upper electrode film. However, the sum of thestresses produced in the upper electrode film and the insulating film iscompressive.

COMPARATIVE EXAMPLE 4

An ink-jet recording head of Comparative Example 4 was manufactured tohave the same structure as that of Example 6, except that the insulatingfilm was not formed.

As shown in Tables 2 and 3, a film formed of platinum produces tensilestress. Therefore, in the ink-jet recording head of Comparative Example4, tensile stress is produced in the upper electrode film. Since theinsulating film which produces stress is not present, the sum of thestresses produced in the upper electrode film and the insulating film istensile.

TABLE 2 Film stress (ε × Y × m) Material and thickness [Pa] (m) [nm]Upper Upper electrode Insulating electrode Insulating film film filmfilm (σ₁) (σ₂) Sum Example 4 Ir: 50 Al₂O₃: 100 −40 −11 −51 Example 5 Pt:50 Al₂O₃: 100 5 −11 −6 Example 6 Pt: 100 Al₂O₃: 100 10 −11 −1Comparative Pt: 100 — 10 — 10 Example 4

TABLE 3 Young's modulus (Y) [Pa] Stress (ε × Y) [Pa] Ir 5.3 × 10¹¹ −8.0× 10⁸ Pt 1.5 × 10¹¹  1.0 × 10⁸ Al₂O₃ 2.0 × 10¹¹ −1.1 × 10⁸

As can be understood from the results shown in Table 2, in the ink-jetrecording heads of Examples 4 to 6, in which the sum of the stress ofthe insulating film and the stress of the upper electrode film iscompressive, the amount of displacement of the vibration plate caused bydrive of the piezoelectric elements is larger than that in the ink-jetrecording head of Comparative Example 4 in which the sum of the stressof the insulating film and the stress of the upper electrode film istensile. As is apparent from this result, a decrease in amount ofdisplacement of the vibration plate caused through drive of thepiezoelectric elements can be prevented through generation of acompressive stress as the sum of the stress of the insulating film andthe stress of the upper electrode film.

In the ink-jet recording head of Example 4, a larger compressive stressis produced as the sum of the stress of the insulating film and thestress of the upper electrode film, as compared with the ink-jetrecording head of Example 5. However, in the ink-jet recording head ofExample 5, the piezoelectric element displaces by a greater amount ascompared with the ink-jet recording head of Example 4. Conceivably, thisphenomenon occurs because, as shown in Tables 2 and 3, the upperelectrode film of Example 5 is formed of platinum, and therefore has aYoung's modulus (hardness) smaller than that of the upper electrode filmof Example 4, which is formed of iridium. As described above, when thesum of the stress of the insulating film and the stress of the upperelectrode film is compressive, the quantity of deformation of thevibration plate can be reduced, and the amount of displacement of thevibration plate caused through drive of the piezoelectric elements canbe increased. As is also apparent from this result, a decrease in amountof displacement of the vibration plate caused through drive of thepiezoelectric elements can be prevented more reliably through generationof a compressive stress as the sum of the stress of the insulating filmand the stress of the upper electrode film.

EMBODIMENT 2

FIG. 7 is a schematic perspective view of an ink-jet recording headaccording to Embodiment 2; and FIG. 8 shows plan and sectional views ofthe ink-jet recording head. FIG. 9 is a plan view showing a main portionof the ink-jet recording head; and FIG. 10 is a pair of sectional viewsshowing the main portion of FIG. 9. In the following description,members identical with those in the above-described embodiment aredenoted by the same reference numerals, and their repeated descriptionsare omitted.

In the present embodiment, at least the constituent layers ofpiezoelectric elements 300 are covered with an insulating film 100Aincluding a first insulating film 101 and a second insulating film 102.Specifically, as shown in FIGS. 7 to 10, a lower electrode film 60 isformed in a region facing pressure generation chambers 12 with respectto the longitudinal direction of the pressure generation chambers 12 andextends continuously through respective regions corresponding to theplurality of pressure generation chambers 12. Piezoelectric layers 70and upper electrode films 80 are basically provided within respectiveregions facing the pressure generation chambers 12. However, withrespect to the longitudinal direction of the pressure generationchambers 12, they extend beyond the end portion of the lower electrodefilm 60, and the end surface of the lower electrode film 60 is coveredby the piezoelectric layers 70. A piezoelectric non-active portion 330,which includes the piezoelectric layer 70 but is not substantiallydriven, is formed in the vicinity of the longitudinal end of eachpressure generation chamber 12 (see FIG. 8( a)).

In the present embodiment, the surfaces of the constituent layers of thepiezoelectric elements 300 are covered with the insulating film 100Aformed of a damp-proofing material, except for connection portions 90 aof upper-electrode lead electrodes 90A and a connection portion 95 a ofa lower-electrode lead electrode 95A. Specifically, as shown in FIGS. 9and 10, the first insulating film 101 is provided in pattern regions ofthe constituent layers of the piezoelectric elements 300. Connectionholes 101 a for connecting the upper-electrode lead electrodes 90A andthe upper electrode films 80 are formed in regions facing the vicinityof the longitudinal end portions of the upper electrode films 80. Aconnection hole 101 b for connecting the lower-electrode lead electrode95A and the lower electrode film 60 is formed outside the row of thepiezoelectric elements 300. That is, at least the pattern regions of theconstituent layers of piezoelectric elements 300 are completely coveredwith the first insulating film 101, except for the connection holes 101a and 101 b.

The upper-electrode lead electrodes 90A to be connected to the upperelectrode films 80 of the piezoelectric elements 300 via the connectionholes 101 a, and the lower-electrode lead electrode 95A to be connectedto the lower electrode film 60 via the connection hole 101 b areprovided on the first insulating film 101. Each upper-electrode leadelectrode 90A extends from the vicinity of one longitudinal end of thecorresponding upper electrode film 80 (in the present embodiment, from aportion corresponding to the piezoelectric non-active portion 330) tothe vicinity of the end portion of the channel substrate 10. Further,the lower-electrode lead electrode 95A extends from a point outside therow of the piezoelectric elements 300 and near the end portion of thelower electrode film 60 to the vicinity of the end portion of thechannel substrate 10. The end portions of the upper-electrode leadelectrodes 90A and the lower-electrode lead electrode 95A serve as theconnection portions 90 a and 95 a, to which the drive wiring 130 isconnected.

Further, the second insulating film 102 is provided on theupper-electrode lead electrodes 90A, the lower-electrode lead electrode95A, and the first insulating film 101. That is, the pattern regions ofthe upper-electrode lead electrodes 90A, the lower-electrode leadelectrode 95A, and the constituent layers of the piezoelectric elements300 are covered with the second insulating film 102, except for regionsfacing the connection portions 90 a of the upper-electrode leadelectrodes 90A and the connection portion 95 a of the lower-electrodelead electrode 95A.

In this structure, by means of the first and second insulating films 101and 102, breakage of the piezoelectric layers 70 due to water (moisture)can be prevented more reliably. Further, the surfaces of the constituentlayers of the piezoelectric elements 300 and the upper-electrode leadelectrodes 90A and the lower-electrode lead electrode 95A are coveredwith the second insulating film 102, except for the connection portions90 a of the upper-electrode lead electrodes 90A and the connectionportion 95 a of the lower-electrode lead electrode 95A. Therefore, evenwhen water enters from the side corresponding to the end portion of thesecond insulating film 102, water can be prevented from reaching thepiezoelectric layers 70, whereby breakage of the piezoelectric layers 70due to water can be reliably prevented.

Further, since the upper-electrode lead electrodes 90A and thelower-electrode lead electrode 95A are formed on the first insulatingfilm 101, electric corrosion does not occur even if wet etching is usedfor formation of the upper-electrode lead electrodes 90A and thelower-electrode lead electrode 95A. Therefore, anomaly in relation toetching speed stemming from electric corrosion or a like anomaly doesnot occur, and the upper-electrode lead electrodes 90A and thelower-electrode lead electrode 95A can be formed with high accuracy.Further, it is possible to prevent breakage of the piezoelectricelements 300, such as exfoliation of the upper electrode films 80, whichwould otherwise occur during etching of the upper-electrode leadelectrodes 90A and the lower-electrode lead electrode 95A, whereby yieldis greatly improved.

The first and second protective films 101 and 102, which constitute theinsulating film 100A, are preferably formed of aluminum oxide (AlO_(x)).The first and second insulating films 101 and 102 may be formed ofdifferent materials; for example, such that the first insulating film101 is formed of silicon oxide, and the second insulating film 102 isformed of aluminum oxide. However, one of the first and secondinsulating films 101 and 102 is preferably formed of aluminum oxide.Also, preferably, at least the second insulating film 102 is formed ofaluminum oxide, and particularly preferably, both the first and secondinsulating films 101 and 102 are formed of aluminum oxide. Through useof aluminum oxide as the material of either or both of the first andsecond insulating films 101 and 102, permeation of water in ahigh-humidity environment can be prevented to a sufficient degree evenwhen the first and second insulating films 101 and 102 are formed tohave a relatively small film thickness. For example, in the case whereboth the first and second insulating films 101 and 102 are formed ofaluminum oxide, permeation of water can be prevented to a sufficientdegree, even when the first and second insulating films 101 and 102 eachhave a film thickness of about 50 nm.

Moreover, when aluminum oxide is used as the material of either or bothof the first and second insulating films 101 and 102, theupper-electrode lead electrodes 90A and the lower-electrode leadelectrode 95A are preferably formed of a material which containsaluminum (Al) as a predominant component. For example, in the presentembodiment, each of the first and second insulating films 101 and 102 isformed of aluminum oxide, and the upper-electrode lead electrodes 90Aand the lower-electrode lead electrode 95A are formed of an alloycontaining 99.5 wt % aluminum (Al) and 0.5 wt % copper (Cu).

With this, the degree of adhesion of the upper-electrode lead electrodes90A and the lower-electrode lead electrode 95A with the first insulatingfilm 101 or the second insulating film 102 increases. Further, in thecase where both the first and second insulating films 101 and 102 areformed of aluminum oxide, not only the degree of adhesion of theupper-electrode lead electrodes 90A and the lower-electrode leadelectrode 95A with the first insulating film 101 or the secondinsulating film 102, but also the degree of adhesion of the firstinsulating film 101 with the second insulating film 102 increases.Accordingly, permeation of water can be prevented more reliably, andbreakage of the piezoelectric elements 300 stemming from water can bereliably prevented over a long period of time. Moreover, even when thefirst and second insulating films 101 and 102 are made relatively thin,permeation of water can be prevented more reliably, and drive of thepiezoelectric elements 300 is not hindered, whereby excellent inkdischarge property can be maintained.

As in the case of Embodiment 1, a protective plate and a compliancesubstrate are bonded to the surface of the channel substrate 10 on theside toward the piezoelectric elements 300. However, the protectiveplate 30A of the present embodiment differs from the protective plate ofEmbodiment 1 in that a through-hole portion is not formed in theprotective plate 30A. As described above, the upper-electrode leadelectrodes 90A and the lower-electrode lead electrode 95A extend to thevicinity of the end portion of the channel substrate 10; i.e., to aposition outside the piezoelectric-element-holding portion 31. Ends ofthe drive wiring 130, which extends from the drive IC 120 mounted on theprotective plate 30, are connected to the connection portions 90 a ofthe upper-electrode lead electrodes 90A and the connection portion 95 aof the lower-electrode lead electrode 95A.

A method for manufacturing the ink-jet recording head according to thepresent embodiment will be described. FIG. 11 is a set of sectionalviews taken along the longitudinal direction of the pressure generationchambers 12. First, as described in Embodiment 1, the elastic film 50and the insulating film 55 are formed on the channel substrate 10, andthe piezoelectric elements 300, each composed of the lower electrodefilm 60, the piezoelectric layer 70, and the upper electrode film 80,are formed on the insulating film 55 (see FIG. 5( a) to FIG. 6( a)).

Subsequently, as shown in FIG. 11( a), the first insulating film 101 ofaluminum oxide is formed, and is then patterned to a predeterminedshape. Specifically, the first insulating film 101 is formed over theentire surface of the channel substrate 10. Subsequently, the firstinsulating film 101 is etched via a predetermined mask so as to form theconnection holes 101 a and 101 b in a region facing the upper electrodefilms 80 and a region facing the lower electrode film 60 outside the rowof the piezoelectric elements 300.

Next, as shown in FIG. 11( b), the upper-electrode lead electrodes 90Aare formed. Specifically, a metal layer 92A formed of a materialcontaining aluminum (Al) as a predominant component is formed over theentire surface of the channel substrate 10. Subsequently, the metallayer 92A is patterned for each piezoelectric element 300 via a maskpattern (not shown) formed of resist or the like, whereby theupper-electrode lead electrodes 90A are formed. Although notillustrated, at that time, the lower-electrode lead electrode 95A isformed simultaneously.

Use of the material containing aluminum as a predominant component asthe material for the metal layer 92A is preferable, because the degreeof adhesion with the first or second insulating film 101 or 102 isimproved, and the ratio of permeation of water to the piezoelectriclayer decreases further. Needless to say, gold (Au) or the like may beused to form the metal layer 92A. However, in such a case, a closecontact layer formed of, for example, titanium tungsten (TiW) isdesirably provided underneath the metal layer. Needless to say, evenwhen the metal layer is formed of aluminum, a close contact layer formedof titanium tungsten may be provided.

Next, as shown in FIG. 11( c), the second insulating film 102 of, forexample, aluminum oxide is formed, and is then patterned to apredetermined shape. Specifically, the second insulating film 102 isformed over the entire surface of the channel substrate 10, and thenremoved from the regions facing the connection portions 90 a of theupper-electrode lead electrodes 90A and the connection portion 95 a ofthe lower-electrode lead electrode 95A. In the present embodiment, thesecond insulating film 102 is formed in substantially the same regionsas those of the first insulating film 101; i.e., only in the patternregions of the constituent layers of the piezoelectric elements 300, theupper-electrode lead electrodes 90A, and the lower-electrode leadelectrode 95A. Needless to say, the second insulating film 102 may beformed on the entire surface other than the regions facing theconnection portions 90 a of the upper-electrode lead electrodes 90A andthe connection portion 95 a of the lower-electrode lead electrode 95A.In either case, the essential requirement is that the second insulatingfilm 102 covers the pattern regions of the constituent layers of thepiezoelectric elements 300, the upper-electrode lead electrodes 90A, andthe lower-electrode lead electrode 95A, except for the connectionportions 90 a of the upper-electrode lead electrodes 90A and theconnection portion 95 a of the lower-electrode lead electrode 95A.

Next, as shown in FIG. 11( d), the protective plate 30 is bonded to thechannel substrate 10 on the side toward the piezoelectric elements 300by use of the adhesive 35. Subsequently, via the mask film 51 patternedto a predetermined shape, the channel substrate 10 is anisotropicallyetched so as to form the pressure generation chambers 12, etc.

EMBODIMENT 3

FIG. 12 is a schematic perspective view of an ink-jet recording headaccording to Embodiment 3; and FIG. 13 shows plan and sectional views ofthe ink-jet recording head. FIG. 14 is a plan view showing a mainportion of the ink-jet recording head.

In the present embodiment, second upper-electrode lead electrodes 96,which constitute a portion of the connection wiring, are furtherprovided. As shown in FIGS. 12 to 14, a lower electrode film 60 isformed in a region facing pressure generation chambers 12 with respectto the longitudinal direction of the pressure generation chambers 12 andextends continuously through respective regions corresponding to theplurality of pressure generation chambers 12. Further, at a locationoutside the row of the pressure generation chambers 12, the lowerelectrode film 60 extends to the vicinity of the end portion of thechannel substrate 10, and the end portion of the extension serves as aconnection portion 60 a, to which connection wiring 130, which extendsfrom a drive IC 120 to be described later, is connected. Piezoelectriclayer 70 and upper electrode films 80 are basically provided withinrespective regions facing the pressure generation chambers 12. However,with respect to the longitudinal direction of the pressure generationchambers 12, they extend beyond the end portion of the lower electrodefilm 60, and the end surface of the lower electrode film 60 is coveredby the piezoelectric layers 70. A piezoelectric non-active portion 330,which includes the piezoelectric layer 70 but is not substantiallydriven, is formed in the vicinity of the longitudinal end of eachpressure generation chamber 12. Further, upper-electrode lead electrodes90A formed of, for example, a material which contains aluminum as apredominant component are connected to ends of the upper electrode films80 of the piezoelectric element 300. In the present embodiment, theupper-electrode lead electrodes 90A extend from a region on thepiezoelectric non-active portions 330, located outside the pressuregeneration chambers 12, to a region on the insulating film 55.

Further, the second upper-electrode lead electrodes 96 are connected tothe upper-electrode lead electrodes 90A via an insulating film 100formed of an inorganic insulating material. The second upper-electrodelead electrodes 96 extend to the vicinity of the end portion of thechannel substrate 10. As in the case of the connection portion 60 a ofthe lower electrode film 60, tip end portions of the secondupper-electrode lead electrodes 96 serves as terminal portions 96 a, towhich the drive wiring 130 is connected.

In the present embodiment, the insulating film 100 is provided in thepattern regions of the constituent layers of piezoelectric elements 300,the upper-electrode lead electrodes 90A, and the second upper-electrodelead electrodes 96. At least the piezoelectric elements 300 and theupper-electrode lead electrodes 90A are covered with the insulating film100, except for the connection portions 90 a of the upper-electrode leadelectrodes 90A. For example, in the present embodiment, the insulatingfilm 100 is continuously formed to cover the lower electrode film 60outside the row of the piezoelectric elements 300, so that the lowerelectrode film 60, together with the piezoelectric elements 300 and theupper-electrode lead electrodes 90A, is covered with the insulating film100, except for the connection portion 60 a.

As described above, the insulating film 100 is continuously formed tothe pattern region of the second upper-electrode lead electrodes 96.That is, the insulating film 100 is continuously formed to the vicinityof the end portion of the channel substrate 10, and the terminalportions 96 a of the second upper-electrode lead electrodes 96 arelocated above the insulating film 100.

As described above, the surfaces of the piezoelectric elements 300 andthe upper-electrode lead electrodes 90A are covered with the insulatingfilm 100, and the terminal portions 96 a, to which the drive wiring 130is connected, are provided on the second upper-electrode lead electrodes96 provided on the insulating film 100. Thus, breakage of thepiezoelectric layer 70 due to water (moisture) can be reliablyprevented. That is, the piezoelectric elements 300 and theupper-electrode lead electrodes 90A (except for the connection portions90 a) are covered with the insulating film 100, which continuouslyextends to the pattern region of the second upper-electrode leadelectrodes 96. Further, the connection portions 90 a of theupper-electrode lead electrodes 90A are covered by the secondupper-electrode lead electrodes 96. Accordingly, water can enter onlyfrom the end portion of the insulating film 100, and even when waterenters, the water is substantially prevented from reaching thepiezoelectric layer 70, whereby breakage of the piezoelectric layer 70due to water can be prevented more reliably.

Further, since the insulating film 100 is provided under the terminalportions 96 a of the second upper-electrode lead electrodes 96, to whichthe drive wiring 130 is connected, there can be attained an effect ofincreasing the degree of adhesion of the second upper-electrode leadelectrodes 96. This prevents occurrence of failures such as exfoliationof the second upper-electrode lead electrodes 96, which exfoliationwould otherwise occur when the drive wiring 130 is connected to thesecond upper-electrode lead electrodes 96 by means of wire bonding orthe like.

In the present embodiment, the end portion of the extension of the lowerelectrode film 60, which extends to the vicinity of the communicationsection 13, serves as the connection portion 60 a for connection withthe connection wring 130. However, for example, a configuration as shownin FIG. 15 may be employed. Specifically, a lower-electrode leadelectrode 95A, which is electrically connected to the lower electrodefilm 60, is provided outside the row of the piezoelectric elements 300such that the lower-electrode lead electrode 95A extends to a regionoutside the piezoelectric elements 300 with respect to the longitudinaldirection thereof. A second lower-electrode lead electrode 99 isprovided such that it extends to the vicinity of the end portion of thechannel substrate 10, and a tip end portion of the secondlower-electrode lead electrode 99 is used as a terminal portion 99 a, towhich the drive wiring 130 is connected. In this case, the patternregions of the constituent layers of the piezoelectric elements 300, theupper-electrode lead electrodes 90A, and the lower-electrode leadelectrode 95A, the second upper-electrode lead electrode 96, and thesecond lower-electrode lead electrode 99 are covered with the insulatingfilm 100, except for the connection portions 90 a and 95 a of the upperand lower-electrode lead electrodes 90A and 95A.

A method for manufacturing the ink-jet recording head according to thepresent embodiment will be described. FIGS. 16 and 17 show sectionalviews taken along the longitudinal direction of the pressure generationchambers 12. As described above, ink-jet recording heads aremanufactured in such a manner that a large number of chips aresimultaneously formed on a single wafer, and the wafer is then dicedinto chips each corresponding to a channel substrate 10 as shown inFIG. 1. In the present embodiment, a method for manufacturing theink-jet recording head by actually using a channel substrate wafer 150,which is a silicon wafer.

First, as shown in FIG. 16( a), the elastic film 50 and the insulatingfilm 55 are formed on the channel substrate wafer 150 (channel substrate10), which is a silicon wafer having a relatively large thickness ofabout 625 μm and high rigidity. Subsequently, the piezoelectric elements300, each composed of the lower electrode film 60, the piezoelectriclayer 70, and the upper electrode film 80, are formed on the insulatingfilm 55. The methods for forming the elastic film 50, the insulatingfilm 55, and the piezoelectric elements 300 are identical to those inEmbodiment 1 (see FIGS. 5( a) to 5(d)).

Next, as shown in FIG. 16( b), the upper-electrode lead electrodes 90Aare formed. Specifically, a metal layer 92A formed of a predeterminedmetal material (aluminum (Al) in the present embodiment) is formed overthe entire surface of the channel substrate wafer 150. After that, themetal layer 92A is patterned for each piezoelectric element 300 via amask pattern (not shown) formed of resist or the like, whereby theupper-electrode lead electrodes 90A are formed.

Next, as shown in FIG. 16( c), the insulating film 100 of aluminum oxide(Al₂O₃) is formed, and is then patterned to a predetermined shape.Specifically, the insulating film 100 is formed over the entire surfaceof the channel substrate wafer 150. Subsequently, the insulating film100 is removed from regions corresponding to the connection portion 60 aof the lower electrode film 60 and the connection portions 90 a of theupper-electrode lead electrodes 90A, whereby openings 100 a are formed.Notably, in the present embodiment, the insulating film 100 is removedfrom regions corresponding to the connection portions 60 a and 90 a, andfrom the remaining region except for the pattern regions of theconstituting layers of the piezoelectric elements 300, theupper-electrode lead electrodes 90A, and the second upper-electrode leadelectrodes 96 formed in a step to be described later. Needless to say,the insulating film 100 may be removed only from the regionscorresponding to the connection portions 60 a and 90 a.

Next, the second upper-electrode lead electrodes 96 are formed. Forexample, in the present embodiment, as shown in FIG. 16( d), a closecontact layer 97 formed of, for example, titanium tungsten (TiW) isformed over the entire surface of the channel substrate wafer 150, and ametal layer 98 formed of, for example, gold (Au) is formed over theentire surface of the close contact layer 97. After that, the metallayer 98 is patterned for each piezoelectric element 300 via a maskpattern (not shown), and the close contact layer 97 is patterned throughetching, whereby the second upper-electrode lead electrodes 96 areformed.

Next, as shown in FIG. 17( a), a protective plate wafer 160, which is asilicon wafer and is to become a plurality of protective plates 30 isbonded to the channel substrate wafer 150 on the side toward thepiezoelectric elements 300. Notably, since this protective plate wafer160 has thickness of, for example, about 625 μm, the rigidity of thechannel substrate wafer 150 greatly increases as a result of boding ofthe protective plate wafer 160.

Subsequently, as shown in FIG. 17( b), in the present embodiment, thechannel substrate wafer 150 is polished until the thickness of thechannel substrate wafer 150 decreases to a certain level. Further, thechannel substrate wafer 150 is wet-etched by use of an aqueous solutioncontaining fluoric acid and nitric acid such that the channel substratewafer 150 has a predetermined thickness. For example, in the presentembodiment, the channel substrate wafer 150 was etched such that thechannel substrate wafer 150 has a thinness of about 70 μm.

After that, as shown in FIG. 17( c), a mask film 52A formed of, forexample, silicon nitride is newly formed on the channel substrate wafer150, and is patterned into a predetermined shape. The pressuregeneration chambers 12, the communication sections 13, the ink supplypassages 14, etc. are formed in the channel substrate wafer 150 byanisotropically etching the channel substrate wafer 150 via the maskfilm 52A.

After that, unnecessary portions of the outer circumferential edges ofthe channel substrate wafer 150 and the protective plate wafer 160 areremoved by cutting them by means of dicing or the like. Subsequently,the nozzle plate 20 having the nozzle orifices 21 formed therein isbonded to the surface of the channel substrate wafer 150 opposite theprotective plate wafer 160, and the compliance substrate 40 is bonded tothe protective plate wafer 160. Subsequently, the channel substratewafer 150, etc. are diced into chips each corresponding to the channelsubstrate 10 as shown in FIG. 1. Thus, the ink-jet recording head of thepresent embedment is completed.

EMBODIMENT 4

FIG. 18 is a pair of sectional views of an ink-jet recording headaccording to Embodiment 4. The present embodiment is an example in whichin the structure of Embodiment 3, the piezoelectric elements 300 arecovered with the insulating film 100A composed of the first insulatingfilm 101 and the second insulating film 102 as in Embodiment 2. That is,in the present embodiment, as shown in FIG. 18, the upper-electrode leadelectrodes 90A are provided on the first insulating film 101 to extendtherealong, and are connected to the upper electrode films 80 via theconnection holes 101 a of the first insulating film 101. Further, thepattern regions of the upper-electrode lead electrodes 90A, and theconstituent layers of the piezoelectric elements 300 are covered withthe second insulating film 102, except for regions facing the connectionportions 90 a of the upper-electrode lead electrodes 90A. The secondinsulating film 102 is further formed on the first insulating film 101,whereby the piezoelectric elements 300 are covered with the first andsecond insulating film 101 and 102. Further, the second upper-electrodelead electrodes 96 are formed on the second insulating film 102, and areconnected to the first upper-electrode lead electrodes 90A via theopenings 102 a of the second insulating film 102.

In such a configuration, the piezoelectric elements 300 are covered withthe first and second insulating film 101 and 102, whereby thepiezoelectric layers 70 are prevented from contacting water (moisture).Accordingly, breakage of the piezoelectric layers 70 due to water(moisture) can be prevented more reliably.

EMBODIMENT 5

FIG. 19 is an exploded perspective view of an ink-jet recording headaccording to Embodiment 5. FIG. 20 shows plan and sectional views of therecording head.

The present embodiment is an example in which a moisture permeableportion formed of a material through which water within thepiezoelectric-element-holding portion can permeate is provided at aportion of a bonding surface of the protective plate, which surface isbonded to the channel substrate. The present embodiment is identical toEmbodiment 1, except that the upper-electrode lead electrodes are formedto extend to the vicinity of the end portion of the channel substrate,the drive wiring is connected to the upper-electrode lead electrodesoutside the protective plate and a through portion is not provided inthe protective plate.

Specifically, as shown in FIGS. 19 and 20, a moisture permeable portion170, which is formed of a material through which water within thepiezoelectric-element-holding portion 31, can permeate is provided at aportion of a bonding surface of the protective plate 30A, which surfaceis bonded to the channel substrate 10, specifically, in a portion of aregion surrounding the piezoelectric-element-holding portion 31 exceptfor a region located on the side toward the reservoir 110. For example,the moisture permeable portion 170 is formed of an adhesive layer 36formed of an adhesive having a water permeability higher than that ofthe adhesive that forms the adhesive layer 35, and as shown in FIG. 20,is provided in a region of the piezoelectric-element-holding portion 31opposite the reservoir 110. Notably, the moisture permeable portion 170(the adhesive layer 36) also plays a role of bonding the protectiveplate 30 and the channel substrate 10 together.

Since the moisture permeable portion 170 is provided, water (moisture)having entered the piezoelectric-element-holding portion 31 isdischarged to the outside via the moisture permeable portion 170.Accordingly, the interior of the piezoelectric-element-holding portion31 is maintained at a relatively low humidity, whereby breakage of thepiezoelectric elements 300 due to water can be prevented. Specifically,since the reservoir 110 is provided adjacent to thepiezoelectric-element-holding portion 31, water of ink stored in thereservoir 110 enters the piezoelectric-element-holding portion 31 viathe adhesive layer 35 in a region of the piezoelectric-element-holdingportion 31 on the reservoir 110 side. Therefore, humidity within thepiezoelectric-element-holding portion 31 increases gradually, and insome cases, the humidity within the piezoelectric-element-holdingportion 31 increases to about 85%. Even when an adhesive having a lowwater permeability is used for forming the adhesive layer 35, such entryof water of ink into the piezoelectric-element-holding portion 31 cannotbe prevented completely.

However, since the moisture permeable portion 170 is provided, even whenwater enters the piezoelectric-element-holding portion 31 via theadhesive layer 35 in the region of the piezoelectric-element-holdingportion 31 on the reservoir 110 side, water within thepiezoelectric-element-holding portion 31 is discharged to the outsidevia the moisture permeable portion 170 if the humidity within thepiezoelectric-element-holding portion 31 is higher than the outsidehumidity. Accordingly, the humidity within thepiezoelectric-element-holding portion 31 is always suppressed to thehumidity of outside air or lower.

Since the surfaces of the upper-electrode lead electrodes 90 and theconstituent layers of the piezoelectric elements 300 sealed within thepiezoelectric-element-holding portion 31 are covered with the insulatingfilm 100 formed of an inorganic insulating material, if the humiditywithin the piezoelectric-element-holding portion 31 is suppressed to alevel close to the humidity of outside air, the piezoelectric elementsare not broken by water (moisture) within thepiezoelectric-element-holding portion 31. Accordingly, an ink-jetrecording head whose piezoelectric elements 300 have considerablyimproved durability can be realized.

A method for manufacturing the ink-jet recording head according to thepresent embodiment will be described. FIG. 21 shows sectional viewstaken along the longitudinal direction of the pressure generationchambers 12. First, as described in Embodiment 1, the elastic film 50and the insulating film 55 are formed on the channel substrate 10, andthe piezoelectric elements 300, each composed of the lower electrodefilm 60, the piezoelectric layer 70, and the upper electrode film 80,are formed on the insulating film 55 (see FIGS. 5( a) to 6(a)).

Next, as shown in FIG. 21( a), a close contact layer 91 and a metallayer 92 are successively formed, and then patterned to thereby form theupper-electrode lead electrodes 90. Subsequently, as shown in FIG. 21(b), the insulating film 100 of, for example, aluminum oxide (Al₂O₃) isformed.

Next, as shown in FIG. 21( c), the protective plate 30 is bonded to thechannel substrate 10 on the side toward the piezoelectric elements 300via the adhesive layer 35, and the moisture permeable portion 170 isformed. That is, the adhesive layer 35 is formed except for a peripheraledge region of the piezoelectric-element-holding portion 31 of theprotective plate 30, the region being located opposite the reservoirsection 32. The adhesive layer 36 having higher water permeability ascompared with the adhesive layer 35 is formed in the region locatedopposite the reservoir section 32. The protective plate 30 is bonded tothe channel substrate 10 via these adhesive layers 35 and 36. Thus, themoisture permeable portion 170 composed of the adhesive layer 36 isformed in the peripheral edge region of thepiezoelectric-element-holding portion 31 opposite the reservoir 110.

After that, as shown in FIG. 21( d), the pressure generation chambers12, etc. are formed by anisotropically etching the channel substrate 10via the mask film 51 patterned to a desired shaped.

EMBODIMENT 6

FIG. 22 is a side view of an ink-jet recording head according toEmbodiment 6. The present embodiment is an example in which a moisturepermeable portion 170A is provided in the protective plate 30A inregions outside the opposite end portions of the row of the pressuregeneration chambers 12. That is, in the present embodiment, as shown inFIG. 22, portions of the protective plate 30 corresponding to theregions outside the opposite end portions of the row of the pressuregeneration chambers 12 are removed by means of half etching so as toform a recessed portion 34. This recessed portion 34 is sealed with apotting material, whereby the moisture permeable portion 170A is formed.

In this structure as well, as in the case of Embodiment 5, water withinthe piezoelectric-element-holding portion 31 is discharged to theoutside via the moisture permeable portion 170A, and the humidity withinthe piezoelectric-element-holding portion 31 is maintained at a levelclose to the outside humidity. Accordingly, breakage of thepiezoelectric elements 300 stemming from water can be prevented for along period of time.

OTHER EMBODIMENTS

In the above, various embodiments of the present invention have beendescribed. However, the present invention is not limited to theabove-described embodiments. For example, in the above-describedEmbodiments 1 to 4, the piezoelectric elements are formed within thepiezoelectric-element-holding portion. However, the present invention isnot limited thereto, and, needless to say, the piezoelectric elementsmay be exposed. In this case as well, since the surfaces of thepiezoelectric elements and the upper-electrode lead electrodes, etc. arecovered with an insulating film formed of an inorganic insulatingmaterial, breakage of the piezoelectric layer stemming from water(moisture) can be reliably prevented. Further, for example, inEmbodiments 5 and 6, the moisture permeable portion 170 is provided at ajoint surface of the protective plate 30, which joined to the channelsubstrate 10. However, the present invention is not limited thereto,and, for example, there can be employed a structure in which acommunication hole communicating the piezoelectric-element-holdingportion 31 is provided on the upper surface of the protective plate 30or the like, and the communication hole is sealed with an organicmaterial such as an adhesive having high water permeability, whereby amoisture permeable portion is formed.

Each of the ink-jet recording heads of the above embodiments partiallyconstitutes a recording head unit, which includes an ink channelcommunicating with an ink cartridge or a like device, to thereby bemounted on an ink-jet recording apparatus. FIG. 23 schematically showsan example of such an ink-jet recording apparatus. As shown in FIG. 23,recording head units 1A and 1B each including an ink-jet recording headremovably carry cartridges 2A and 2B, respectively. The cartridges 2Aand 2B serve as ink supply means. A carriage 3 that carries therecording head units 1A and 1B is mounted, in an axially movablecondition, on a carriage shaft 5, which is attached to an apparatus body4. The recording head units 1A and 1B are adapted to discharge, forexample, a black ink composition and a color ink composition,respectively. Driving force of a drive motor 6 is transmitted to thecarriage 3 via a plurality of unillustrated gears and a timing belt 7,whereby the carriage 3, which carries the recording head units 1A and1B, is moved along the carriage shaft 5. A platen 8 is provided on theapparatus body 4 in such a manner as to extend along the carriage shaft5. A recording sheet S is fed onto the platen 8. The recording sheet Sis, for example, paper, which is fed by means of unillustrated paperfeed rollers.

In the above-described embodiments, the present invention has beendescribed while mentioning an ink-jet recording head for discharging inkas a liquid-jet head. However, the basic structure of the liquid-jethead is not limited to those described above. The present invention isintended for application to various liquid-jet heads, and can be appliedto those which discharge liquid other than ink. Examples of otherliquid-jet heads include a recording head for use in image recordingapparatus such as printers; a head for discharging liquid that containscolor materials for use in manufacture of color filters for liquidcrystal displays and the like; a head for discharging liquid thatcontains electrode materials for use in manufacture of electrodes fororganic EL displays, FEDs (field emission displays), and the like; and ahead for discharging liquid that contains, bioorganic compounds for usein manufacture of biochips.

1. A liquid-jet head comprising: a channel substrate which has pressuregeneration chambers formed therein and communicating nozzle orifices fordischarging liquid droplets; and piezoelectric elements each of which iscomposed of a lower electrode, a piezoelectric layer, and an upperelectrode and which are disposed on one surface of the channel substratevia a vibration plate, wherein at least pattern regions of therespective layers which constitute the piezoelectric elements arecovered with an insulating film, and wherein the sum of stress of theinsulating film and stress of the upper electrode is compressive.
 2. Theliquid-jet head according to claim 1, wherein stress of the insulatingfilm and stress of the upper electrode are each compressive.
 3. Theliquid-jet head according to claim 2, wherein the upper electrode isformed of at least Pt.
 4. A liquid-jet apparatus characterized bycomprising the liquid-jet head according to claim
 3. 5. A liquid-jetapparatus characterized by comprising the liquid-jet head according toclaim
 2. 6. The liquid-jet head according to claim 1, wherein stress ofthe insulating film is compressive, and stress of the upper electrode istensile.
 7. The liquid-jet head according to claim 6, wherein the upperelectrode is formed of at least Ir.
 8. A liquid-jet apparatuscharacterized by comprising the liquid-jet head according to claim
 7. 9.The liquid-jet head according to claim 6, wherein stress δ of the upperelectrode and that of the insulating film are each represented by theproduct (ε×Y×m) of Young's modulus of elasticity Y, distortion ε, andfilm thickness m, and stress δ₁ of the upper electrode and stress δ₂ ofthe insulating film satisfy the condition |δ₁|<|δ₂|.
 10. A liquid-jetapparatus characterized by comprising the liquid-jet head according toclaim
 9. 11. A liquid-jet apparatus characterized by comprising theliquid-jet head according to claim
 6. 12. The liquid-jet head accordingto claim 1, wherein a protective plate having apiezoelectric-element-holding portion, which is a space for protectingthe piezoelectric elements, is bonded to a surface of the channelsubstrate via an adhesive layer, the surface being located on the sidetoward the piezoelectric elements, the protective plate includes a flowpassage for liquid to be supplied to the pressure generation chambers,the adhesive layer located on the flow passage side of thepiezoelectric-element-holding portion is exposed to the interior of theflow passage, and a moisture permeable portion which enables permeationof water within the piezoelectric-element-holding portion is provided ina region other than the flow passage side of thepiezoelectric-element-holding portion.
 13. The liquid-jet head accordingto claim 12, wherein the moisture permeable portion is formed of anorganic material.
 14. A liquid-jet apparatus characterized by comprisingthe liquid-jet head according to claim
 13. 15. The liquid-jet headaccording to claim 12, wherein the moisture permeable portion isprovided on a portion of a bonding surface of the protective plate, thebonding surface being bonded to the channel substrate.
 16. Theliquid-jet head according to claim 15, wherein the moisture permeableportion is formed of an adhesive having a water permeability higher thanthat of an adhesive which constitutes the adhesive layer.
 17. Aliquid-jet apparatus characterized by comprising the liquid-jet headaccording to claim
 16. 18. A liquid-jet apparatus characterized bycomprising the liquid-jet head according to claim
 16. 19. The liquid-jethead according to claim 12, wherein the moisture permeable portion isprovided on an upper surface of the protective plate.
 20. A liquid-jetapparatus characterized by comprising the liquid-jet head according toclaim
 19. 21. The liquid-jet head according to claim 12, wherein themoisture permeable portion is formed of a potting material.
 22. Aliquid-jet apparatus characterized by comprising the liquid-jet headaccording to claim
 21. 23. The liquid-jet head according to claim 12,wherein the moisture permeable portion is provided in a region on a sideof the piezoelectric-element-holding portion opposite the flow passage.24. A liquid-jet apparatus characterized by comprising the liquid-jethead according to claim
 23. 25. The liquid-jet head according to claim12, wherein the moisture permeable portion is provided on the protectiveplate in each of regions outside the opposite ends of the row ofpressure generation chambers.
 26. A liquid-jet apparatus characterizedby comprising the liquid-jet head according to claim
 25. 27. Aliquid-jet apparatus characterized by comprising the liquid-jet headaccording to claim
 12. 28. A liquid-jet apparatus characterized bycomprising the liquid-jet head according to claim
 1. 29. The liquid-jethead according to claim 1, wherein the insulating film is formed of aninorganic amorphous material.
 30. A liquid-jet head comprising: achannel substrate which has pressure generation chambers formed thereinand communicating nozzle orifices for discharging liquid droplets; andpiezoelectric elements each of which is composed of a lower electrode, apiezoelectric layer, and an upper electrode and which are disposed onone surface of the channel substrate via a vibration plate, and anupper-electrode lead electrode extending from the upper electrode,wherein at least pattern regions of the respective layers whichconstitute the piezoelectric elements are covered with an insulatingfilm, and wherein at least pattern regions of the respective layerswhich constitute the piezoelectric elements and the upper-electrode leadelectrode are covered with the insulating film, except for regionsfacing connection portions of the lower electrode and theupper-electrode lead electrode, the connection portions being used forconnection with connection wiring through which the piezoelectricelements are driven.
 31. The liquid-jet head according to claim 30,wherein the upper-electrode lead electrode is formed of a materialcontaining aluminum as a predominant component.
 32. A liquid-jetapparatus characterized by comprising the liquid-jet head according toclaim
 31. 33. The liquid-jet head according to claim 30, furthercomprising a lower-electrode lead electrode extending from the lowerelectrode, wherein the lower electrode is connected to the connectionwiring via the lower-electrode lead electrode, and the pattern regioncontaining the lower-electrode lead electrode is covered with theinsulating film, except for regions of the upper-electrode leadelectrode and the lower-electrode lead electrode facing the connectionwiring.
 34. A liquid-jet apparatus characterized by comprising theliquid-jet head according to claim
 33. 35. The liquid-jet head accordingto claim 30, wherein the upper electrode and the upper-electrode leadelectrode are formed of different materials.
 36. A liquid-jet apparatuscharacterized by comprising the liquid-jet head according to claim 35.37. The liquid-jet head according to claim 30, wherein the piezoelectriclayer and the upper electrode of each piezoelectric element extend tothe outside of a region facing the corresponding pressure generationchamber so that a piezoelectric non-active portion is formed, and an endportion of the upper-electrode lead electrode on the side toward theupper electrode is located on the piezoelectric non-active portion andoutside the pressure generation chamber.
 38. A liquid-jet apparatuscharacterized by comprising the liquid-jet head according to claim 37.39. The liquid-jet head according to claim 30, wherein in a state inwhich the connection wiring is connected, the connection portions arecovered with a sealing material formed of an organic insulatingmaterial.
 40. A liquid-jet apparatus characterized by comprising theliquid-jet head according to claim
 39. 41. The liquid-jet head accordingto claim 30, wherein the insulating film includes a first insulatingfilm and a second insulating film, the piezoelectric elements arecovered by the first insulating film except for the connection portionfor connection with the upper-electrode lead electrode, theupper-electrode lead electrode is provided on the first insulating film,and at least the pattern regions of the respective layers whichconstitute the piezoelectric elements and the upper-electrode leadelectrode are covered with the second insulating film except for regionsfacing the connection portions.
 42. A liquid-jet apparatus characterizedby comprising the liquid-jet head according to claim
 41. 43. Theliquid-jet head according to claim 30, wherein the connection wiringincludes a second upper-electrode lead electrode extending from theupper-electrode lead electrode, the second upper-electrode leadelectrode is provided on the insulating film and is connected to theupper-electrode lead electrode at the connection portion, and a terminalportion to which drive wring is connected is provided at a tip endportion of the second upper-electrode lead electrode.
 44. A liquid-jetapparatus characterized by comprising the liquid-jet head according toclaim
 43. 45. The liquid-jet head according to claim 30, wherein thepiezoelectric layer and the upper electrode of each piezoelectricelement extend to the outside of a region facing the correspondingpressure generation chamber so that a piezoelectric non-active portionis formed, and an upper-electrode-side end portion of theupper-electrode lead electrode which is connected to the upper electrodeis located on the piezoelectric non-active portion and outside thepressure generation chamber.
 46. A liquid-jet apparatus characterized bycomprising the liquid-jet head according to claim
 45. 47. The liquid-jethead according to claim 30, wherein a protective plate having apiezoelectric-element-holding portion, which is a space for protectingthe piezoelectric elements, is bonded to a surface of the channelsubstrate, the surface being located on the side toward thepiezoelectric elements, and the connection portion of theupper-electrode lead electrode is provided outside thepiezoelectric-element-holding portion.
 48. A liquid-jet apparatuscharacterized by comprising the liquid-jet head according to claim 47.49. A liquid-jet apparatus characterized by comprising the liquid-jethead according to claim
 30. 50. The liquid-jet head according to claim30, wherein the insulating film is formed of an inorganic amorphousmaterial.
 51. A method of manufacturing a liquid-jet head, comprising:forming piezoelectric elements, each of which is composed of a lowerelectrode, a piezoelectric layer, and an upper electrode, on one surfaceof a channel substrate via a vibration plate, the channel substratehaving pressure generation chambers formed therein and communicatingnozzle orifices for discharging liquid droplets; forming anupper-electrode lead electrode extending from the upper electrode ofeach piezoelectric element; forming an insulating film of an inorganicamorphous material over the entirety of a surface of the channelsubstrate, the surface facing the piezoelectric elements; and patterningthe insulating film such that at least connection-wiring connectionportions of the lower electrode and the upper-electrode lead electrodeare exposed, and the insulating film is left in pattern regions of therespective layers of the piezoelectric elements and the upper-electrodelead electrode, except for the connection portion, wherein the methodincludes, after the patterning the insulating film, bonding a protectiveplate to a surface of the channel substrate, the surface facing thepiezoelectric elements, the protective plate including apiezoelectric-element-holding portion for protecting the piezoelectricelements and a flow passage for liquid to be supplied to the pressuregeneration chambers, wherein in the bonding the protective plate, anadhesive is applied to the protective plate such that a space portion isleft in a portion of a region surrounding thepiezoelectric-element-holding portion, except for a region located onthe side toward the flow passage, the protective plate is bonded to thechannel substrate, and the space portion is sealed by a material havinga water permeability higher than that of the adhesive so as to form amoisture permeable portion through which water within thepiezoelectric-element-holding portion permeates.
 52. A method ofmanufacturing a liquid-jet head according to claim 51, wherein theinsulating film is formed of an inorganic amorphous material.